U.S. patent application number 16/526920 was filed with the patent office on 2020-02-13 for controller and control method for internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hirokazu ANDO, Hirofumi HASHINOKUCHI, Yuto IKEDA, Eiji IKUTA, Yuki NOSE, Yoshiyuki SHOGENJI, Tatsuaki SUZUKI.
Application Number | 20200049043 16/526920 |
Document ID | / |
Family ID | 69405601 |
Filed Date | 2020-02-13 |
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United States Patent
Application |
20200049043 |
Kind Code |
A1 |
NOSE; Yuki ; et al. |
February 13, 2020 |
CONTROLLER AND CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE
Abstract
A controller for an internal combustion engine includes a fuel
introduction process of introducing an air-fuel mixture containing
fuel injected by a fuel injection valve into an exhaust passage
without burning the air-fuel mixture in a cylinder. The fuel
introduction processor is configured to perform, during the
execution of the fuel introduction process, a determination process
of determining whether afterfire, in which the air-fuel mixture
burns at an upstream side of a three-way catalyst device in the
exhaust passage, has occurred and a stopping process of stopping
the fuel introduction process when determining in the determination
process that the afterfire has occurred.
Inventors: |
NOSE; Yuki; (Kasugai-shi,
JP) ; IKEDA; Yuto; (Toyota-shi, JP) ;
HASHINOKUCHI; Hirofumi; (Toyota-shi, JP) ; SUZUKI;
Tatsuaki; (Okazaki-shi, JP) ; IKUTA; Eiji;
(Oobu-shi, JP) ; SHOGENJI; Yoshiyuki; (Toyota-shi,
JP) ; ANDO; Hirokazu; (Kariya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
69405601 |
Appl. No.: |
16/526920 |
Filed: |
July 30, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 3/2066 20130101;
F01N 3/0253 20130101; F01N 2560/06 20130101; F01N 2560/025
20130101; F01N 2610/02 20130101; F01N 2900/1602 20130101; F02D
37/02 20130101; F01N 2430/06 20130101; F01N 2430/085 20130101; F01N
2900/1804 20130101; F01N 3/208 20130101; F01N 2560/026 20130101;
F01N 2610/146 20130101; F02D 41/34 20130101; F01N 2240/16 20130101;
F01N 3/2033 20130101; F02D 41/2454 20130101; F01N 3/22 20130101;
F01N 2900/0602 20130101; F01N 3/0814 20130101; F01N 3/0842
20130101; F02D 41/30 20130101; F01N 9/00 20130101; F02D 41/1441
20130101; F01N 3/101 20130101; F01N 3/0871 20130101; F02D 41/123
20130101; F02D 41/1439 20130101; F02D 41/1454 20130101; F01N 3/2013
20130101; F01N 11/00 20130101; F02D 41/1446 20130101; F01N 3/206
20130101; F02D 41/146 20130101; F01N 3/30 20130101; F01N 2900/1812
20130101; F02D 41/042 20130101 |
International
Class: |
F01N 3/025 20060101
F01N003/025; F02D 41/30 20060101 F02D041/30; F01N 3/10 20060101
F01N003/10; F01N 3/20 20060101 F01N003/20; F02D 37/02 20060101
F02D037/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2018 |
JP |
2018-148058 |
Claims
1. A controller configured to control an internal combustion
engine, the internal combustion engine includes: a fuel injection
valve; a cylinder into which air-fuel mixture containing fuel
injected by the fuel injection valve is introduced; an ignition
device that ignites the air-fuel mixture introduced into the
cylinder with a spark; an exhaust passage through which gas
discharged out of the cylinder flows; and a three-way catalyst
device arranged in the exhaust passage, wherein the controller
comprises a fuel introduction processor configured to execute a
fuel introduction process of introducing the air-fuel mixture,
which contains the fuel injected by the fuel injection valve, into
the exhaust passage without burning the air-fuel mixture in the
cylinder, and the fuel introduction processor is configured to
perform: a determination process of determining, during the
execution of the fuel introduction process, whether afterfire, in
which the air-fuel mixture burns at an upstream side of the
three-way catalyst device in the exhaust passage, has occurred; and
a stopping process of stopping, during the execution of the fuel
introduction process, the fuel introduction process when
determining in the determination process that the afterfire has
occurred.
2. The controller according to claim 1, wherein the internal
combustion engine includes an air-fuel ratio sensor arranged at the
upstream side of the three-way catalyst device in the exhaust
passage, and the determination process is performed by determining
that the afterfire has occurred when an air-fuel ratio detection
value of the air-fuel ratio sensor is a value corresponding to a
richer air-fuel ratio than a specified determination value.
3. The controller according to claim 1, wherein the internal
combustion engine includes an exhaust temperature sensor arranged
at the upstream side of the three-way catalyst device in the
exhaust passage, and the determination process is performed by
determining that the afterfire has occurred when a temperature
detection value of the exhaust temperature sensor is greater than
or equal to a specified determination value.
4. The controller according to claim 1, wherein the internal
combustion engine includes a NOx sensor arranged at a downstream
side of the three-way catalyst device in the exhaust passage, and
the determination process is performed by determining that the
afterfire has occurred when a NOx concentration detection value of
the NOx sensor is greater than or equal to a specified
determination value.
5. The controller according to claim 1, wherein the fuel
introduction processor is configured to, when stopping the fuel
introduction process in accordance with the determination that the
afterfire has occurred, restrict the fuel introduction process from
being further executed until an ignition is turned off.
6. The controller according to claim 1, wherein the fuel
introduction processor is configured to reduce a fuel injection
amount of the fuel injection valve when executing the fuel
introduction process after the determination in the determination
process that the afterfire has occurred.
7. The controller according to claim 1, comprising an air-fuel
ratio control unit configured to: perform, during a combustion
operation of the internal combustion engine, an air-fuel ratio
feedback control of a fuel injection amount based on an air-fuel
ratio detection value of an air-fuel ratio sensor arranged at the
upstream side of the three-way catalyst device in the exhaust
passage; learn an air-fuel ratio learning value in accordance with
a correction value of the fuel injection amount by the air-fuel
ratio feedback control; and relearn the air-fuel ratio learning
value when determining in the determination process that the
afterfire has occurred.
8. The controller according to claim 1, wherein the fuel
introduction processor is configured to record, as diagnostic
information, a number of times the fuel introduction process has
been stopped in accordance with a determination result of the
determination result.
9. A method for controlling an internal combustion engine, wherein
the internal combustion engine includes: a fuel injection valve; a
cylinder into which air-fuel mixture containing fuel injected by
the fuel injection valve is introduced; an ignition device that
ignites the air-fuel mixture introduced into the cylinder with a
spark; an exhaust passage through which gas discharged out of the
cylinder flows; and a three-way catalyst device arranged in the
exhaust passage, wherein the method comprises: executing a fuel
introduction process of introducing the air-fuel mixture, which
contains the fuel injected by the fuel injection valve, into the
exhaust passage without burning the air-fuel mixture in the
cylinder; determining, during the execution of the fuel
introduction process by the fuel introduction processor, whether
afterfire, in which the air-fuel mixture burns at an upstream side
of the three-way catalyst device in the exhaust passage, has
occurred; and stopping, during the execution of the fuel
introduction process by the fuel introduction processor, the fuel
introduction process when determining in the determination process
that the afterfire has occurred.
10. A controller configured to control an internal combustion
engine, wherein the internal combustion engine includes: a fuel
injection valve; a cylinder into which air-fuel mixture containing
fuel injected by the fuel injection valve is introduced; an
ignition device that ignites the air-fuel mixture introduced into
the cylinder with a spark; an exhaust passage through which gas
discharged out of the cylinder flows; and a three-way catalyst
device arranged in the exhaust passage, wherein the controller
includes processing circuitry configured to execute: a fuel
introduction process of introducing the air-fuel mixture, which
contains the fuel injected by the fuel injection valve, into the
exhaust passage without burning the air-fuel mixture in the
cylinder; a determination process of determining, during execution
of the fuel introduction process by the fuel introduction
processor, whether afterfire, in which the air-fuel mixture burns
at an upstream side of the three-way catalyst device in the exhaust
passage, has occurred; and a stopping process of stopping, during
the execution of the fuel introduction process by the fuel
introduction processor, the fuel introduction process when
determining in the determination process that the afterfire has
occurred.
Description
BACKGROUND
1. Field
[0001] The following description relates to a controller and a
control method for a spark-ignition internal combustion engine in
which a three-way catalyst device is arranged in an exhaust
passage.
2. Description of Related Art
[0002] A spark-ignition internal combustion engine performs
combustion by igniting, with a spark of an ignition plug, the
mixture of air and fuel introduced into a cylinder. The combustion
of some of the fuel in the air-fuel mixture may be incomplete,
thereby generating carbonaceous particulate matter (hereinafter
referred to as PM).
[0003] U.S. Patent Application Publication No. 2014/0041362
discloses an onboard spark-ignition internal combustion engine
including a three-way catalyst device arranged in an exhaust
passage and a PM-capturing filter arranged at the downstream side
of the three-way catalyst device in the exhaust passage. In such an
internal combustion engine, PM generated in the cylinder is
captured by a filter to restrict the PM from being released to the
outside. The captured PM gradually deposits in the filter. Thus, if
the deposition is left, the deposited PM may eventually clog the
filter.
[0004] The internal combustion engine executes a fuel introduction
process of increasing the temperature of the three-way catalyst
device while the vehicle is coasting, thereby burning and removing
the PM deposited in the filter. In the fuel introduction process,
fuel injection is executed with the spark of the ignition plug
stopped. This introduces the air-fuel mixture to the exhaust
passage without burning the air-fuel mixture in the cylinder. The
unburned air-fuel mixture introduced into the exhaust passage flows
into the three-way catalyst device and burns in the three-way
catalyst device. When the heat generated by the combustion
increases the temperature of the three-way catalyst device, the
temperature of the gas flowing out of the three-way catalyst into
the filter increases. When the high-temperature heat increases the
temperature of the filter to be higher than or equal to the
ignition point of the PM, the PM deposited in the filter is burned
and removed.
[0005] During the combustion operation of the internal combustion
engine, an air-fuel ratio sensor arranged in the exhaust passage
detects the air-fuel ratio of the air-fuel mixture burned in the
cylinder, and an air-fuel ratio feedback control is executed to
correct the fuel injection amount in accordance with the detection
result of the air-fuel ratio. Then, the air-fuel ratio feedback
control is performed to compensate for the deviation of the fuel
injection amount of the fuel injection valve. In contrast, the
air-fuel ratio feedback control cannot be performed through the
fuel introduction process of stopping combustion in the cylinder.
Thus, the amount of fuel actually injected by the fuel injection
valve (actual injection amount) may deviate from the amount
instructed by the controller (instructed injection amount). As a
result, the actual injection amount is larger than the instructed
injection amount, thereby increasing the fuel concentration of
unburned air-fuel mixture introduced into the exhaust passage. This
may cause afterfire, in which the air-fuel mixture burns in the
exhaust passage before flowing into the three-way catalyst device.
When afterfire occurs continuously, the surface of the catalyst is
exposed to high-temperature heat, thereby deteriorating the
three-way catalyst device. Additionally, the continuous occurrence
of afterfire produces annoying combustion noise.
SUMMARY
[0006] A first aspect provides a controller configured to control
an internal combustion engine. The internal combustion engine
includes a fuel injection valve, a cylinder into which air-fuel
mixture containing fuel injected by the fuel injection valve is
introduced, an ignition device that ignites the air-fuel mixture
introduced into the cylinder with a spark, an exhaust passage
through which gas discharged out of the cylinder flows, and a
three-way catalyst device arranged in the exhaust passage. The
controller includes a fuel introduction processor configured to
execute a fuel introduction process of introducing the air-fuel
mixture, which contains the fuel injected by the fuel injection
valve, into the exhaust passage without burning the air-fuel
mixture in the cylinder. The fuel introduction processor is
configured to perform a determination process of determining,
during the execution of the fuel introduction process, whether
afterfire, in which the air-fuel mixture burns at an upstream side
of the three-way catalyst device in the exhaust passage, has
occurred and a stopping process of stopping, during the execution
of the fuel introduction process, the fuel introduction process
when determining in the determination process that the afterfire
has occurred.
[0007] In the controller for the internal combustion engine, when
afterfire occurred during the execution of the fuel introduction
process, the fuel introduction process is stopped at the point in
time afterfire occurs. This stops introducing unburned air-fuel
mixture into the exhaust passage. Thus, even if afterfire occurs
during the fuel introduction process, continuation of the afterfire
is limited.
[0008] During the execution of the fuel introduction process,
unburned air-fuel mixture containing a large amount of oxygen flows
into a section arranged at the upstream side of the three-way
catalyst device in the exhaust passage. At this time, when
afterfire occurs, the oxygen in the air-fuel mixture is consumed
through the combustion. Thus, in a case in which the air-fuel ratio
sensor is arranged at the upstream side of the three-way catalyst
device in the exhaust passage, when afterfire occurs during the
execution of the fuel introduction process, the air-fuel ratio
detection value of the air-fuel ratio sensor is changed to the rich
side. Accordingly, the determination process can be executed by
determining that afterfire has occurred when the air-fuel ratio
detection value of the air-fuel ratio sensor, which is arranged at
the upstream side of the three-way catalyst device in the exhaust
passage, is a value corresponding to a richer air-fuel ratio than a
specified determination value.
[0009] Additionally, when afterfire occurs, the temperature of gas
increases at a section where the afterfire occurs. Accordingly, the
determination process can be executed by determining that afterfire
has occurred when the temperature detection value of the exhaust
temperature sensor, which is arranged at the upstream side of the
three-way catalyst device in the exhaust passage, is greater than
or equal to a specified determination value.
[0010] NOx, which is a product formed when air-fuel mixture is
burned, is scarcely generated in a slow combustion in the three-way
catalyst device during the fuel feeding process. In contrast, a
large amount of NOx is generated by an intense combustion of
afterfire. Accordingly, the determination process can be executed
by determining that afterfire has occurred when the NOx
concentration detection value of the NOx sensor, which is arranged
at the downstream side of the three-way catalyst device in the
exhaust passage, is greater than or equal to a specified
determination value.
[0011] When the actual injection amount of the fuel introduction
process deviates so as to be larger than the instructed injection
amount, the fuel concentration of the air-fuel mixture introduced
into the exhaust passage during the fuel introduction process
becomes high. Thus, afterfire is likely to occur. Such a deviation
of the fuel injection amount is not eliminated even after the fuel
introduction process is stopped. This may cause afterfire to recur
when the fuel introduction process is further executed. When the
fuel feeding process is stopped in accordance with the
determination that afterfire has occurred, the fuel feeding
processor restricts the fuel feeding processes from being further
executed. This prevents the recurrence of afterfire. The recurrence
of afterfire can also be prevented by reducing the fuel injection
amount of the fuel injection valve when executing the fuel
introduction process after determining by the fuel introduction
processor in the determination process that afterfire has
occurred.
[0012] During the fuel introduction process, afterfire is likely to
occur when the actual injection amount of the fuel injection valve
is deviated such that the actual injection amount is larger than
the instructed injection amount. In some internal combustion
engines, during the combustion operation, the air-fuel ratio
feedback control of the fuel injection amount is performed, and the
air-fuel ratio learning value is learned in accordance with the
correction value of the fuel injection amount by the air-fuel ratio
feedback control. In such a case, if a proper value is learned for
the air-fuel ratio learning value, the actual injection amount of
the fuel injection valve deviates from the instructed injection
amount of the fuel injection valve. Thus, when afterfire occurs
during the fuel introduction process, an improper value may be
learned for the air-fuel ratio learning value. Accordingly, it is
preferred that during the combustion operation of the internal
combustion engine, the controller for the internal combustion
engine performs the air-fuel ratio feedback control of the fuel
injection amount based on the air-fuel ratio detection value of the
air-fuel ratio sensor arranged at the upstream side of the
three-way catalyst device in the exhaust passage. It is also
preferred that when the internal combustion engine includes the
air-fuel ratio control unit, which learns the air-fuel ratio
learning value in accordance with the correction value of the fuel
injection amount by the air-fuel ratio feedback control, the
air-fuel ratio learning value be relearned when determining in the
determination process that afterfire has occurred.
[0013] Additionally, the fuel introduction processor should simply
be configured to record, as diagnosis information, a number of
times the fuel introduction process has been stopped in accordance
with the determination result of the determination process. In such
a case, the information of the number of times of stopping the fuel
introduction processor, which is recorded by the fuel introduction
processor, can be used for a purpose of, for example, identifying
where fault occurs during maintenance.
[0014] A second aspect provides a method for controlling an
internal combustion engine. The internal combustion engine includes
a fuel injection valve, a cylinder into which air-fuel mixture
containing fuel injected by the fuel injection valve is introduced,
an ignition device that ignites the air-fuel mixture introduced
into the cylinder with a spark, an exhaust passage through which
gas discharged out of the cylinder flows, and a three-way catalyst
device arranged in the exhaust passage. The method includes
executing a fuel introduction process of introducing the air-fuel
mixture, which contains the fuel injected by the fuel injection
valve, into the exhaust passage without burning the air-fuel
mixture in the cylinder, determining, during the execution of the
fuel introduction process by the fuel introduction processor,
whether afterfire, in which the air-fuel mixture burns at an
upstream side of the three-way catalyst device in the exhaust
passage, has occurred, and stopping, during the execution of the
fuel introduction process by the fuel introduction processor, the
fuel introduction process when determining in the determination
process that the afterfire has occurred.
[0015] A third aspect provides a controller configured to control
an internal combustion engine. The internal combustion engine
includes a fuel injection valve, a cylinder into which air-fuel
mixture containing fuel injected by the fuel injection valve is
introduced, an ignition device that ignites the air-fuel mixture
introduced into the cylinder with a spark, an exhaust passage
through which gas discharged out of the cylinder flows, and a
three-way catalyst device arranged in the exhaust passage. The
controller includes processing circuitry configured to execute a
fuel introduction process of introducing the air-fuel mixture,
which contains the fuel injected by the fuel injection valve, into
the exhaust passage without burning the air-fuel mixture in the
cylinder, a determination process of determining, during execution
of the fuel introduction process by the fuel introduction
processor, whether afterfire, in which the air-fuel mixture burns
at an upstream side of the three-way catalyst device in the exhaust
passage, has occurred, and a stopping process of stopping, during
the execution of the fuel introduction process by the fuel
introduction processor, the fuel introduction process when
determining in the determination process that the afterfire has
occurred.
[0016] Other features and aspects will be apparent from the
following detailed description, the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram showing the configuration of a
controller for an internal combustion engine according to a first
embodiment and a second embodiment.
[0018] FIG. 2 is a flowchart showing a procedure executed by a fuel
introduction processor from the beginning to the end of a fuel
introduction process in the controller for the internal combustion
engine according to the first embodiment.
[0019] FIG. 3 is a time chart showing an example of how the fuel
introduction process is performed.
[0020] FIG. 4 is a flowchart showing a procedure executed by the
fuel introduction processor from the beginning to the end of the
fuel introduction process in the controller for the internal
combustion engine according to the second embodiment.
[0021] FIG. 5 is a schematic diagram showing the arrangement of
sensors other than the air-fuel ratio sensor that can be used for a
determination process.
[0022] FIG. 6 is a time chart showing an example of how a catalyst
temperature-increasing control is executed when it is determined
whether afterfire has occurred based on a temperature detection
value of the exhaust temperature sensor.
[0023] FIG. 7 is a time chart showing an example of how a catalyst
temperature-increasing control is executed when it is determined
whether afterfire has occurred based on a NOx concentration
detection value of the NOx sensor.
[0024] Throughout the drawings and the detailed description, the
same reference numerals refer to the same elements. The drawings
may not be to scale, and the relative size, proportions, and
depiction of elements in the drawings may be exaggerated for
clarity, illustration, and convenience.
DETAILED DESCRIPTION
[0025] This description provides a comprehensive understanding of
the methods, apparatuses, and/or systems described. Modifications
and equivalents of the methods, apparatuses, and/or systems
described are apparent to one of ordinary skill in the art.
Sequences of operations are exemplary, and may be changed as
apparent to one of ordinary skill in the art, with the exception of
operations necessarily occurring in a certain order. Descriptions
of functions and constructions that are well known to one of
ordinary skill in the art may be omitted.
[0026] Exemplary embodiments may have different forms, and are not
limited to the examples described. However, the examples described
are thorough and complete, and convey the full scope of the
disclosure to one of ordinary skill in the art.
First Embodiment
[0027] A controller for an internal combustion engine according to
a first embodiment will now be described in detail with reference
to FIGS. 1 to 3.
[0028] As shown in FIG. 1, an internal combustion engine 10 mounted
on a vehicle includes a cylinder 12, which accommodates a piston 11
such that the piston 11 can reciprocate. The piston 11 is coupled
to a crankshaft 14 via a connecting rod 13. The reciprocating
motion of the piston 11 in the cylinder 12 is converted into
rotation of the crankshaft 14.
[0029] The cylinder 12 is connected to an intake passage 15,
through which air is introduced into the cylinder 12. The intake
passage 15 is provided with an airflow meter 16, which detects the
flow rate of the air flowing through the intake passage 15 (intake
air amount GA). A throttle valve 17 is provided at the downstream
side of the airflow meter 16 in the intake passage 15. Further, a
fuel injection valve 18 is provided at the downstream side of the
throttle valve 17 in the intake passage 15. The fuel injection
valve 18 injects fuel into the air flowing through intake passage
15 to form mixture of air and fuel.
[0030] The cylinder 12 has an intake valve 19, which connects and
disconnects the intake passage 15 to and from the cylinder 12.
Air-fuel mixture is introduced from the intake passage 15 to the
cylinder 12 when the intake valve 19 opens. The cylinder 12 is
provided with an ignition device 20, which ignites and burns the
air-fuel mixture in the cylinder 12 with a spark.
[0031] The cylinder 12 is connected to an exhaust passage 21, which
discharges exhaust gas generated by combustion of air-fuel mixture.
The cylinder 12 has an exhaust valve 22, which connects and
disconnects the exhaust passage 21 to and from the cylinder 12. The
exhaust gas is introduced from the cylinder 12 into the exhaust
passage 21 when the exhaust valve 22 opens. The exhaust passage 21
is provided with a three-way catalyst device 23, which oxidizes CO
and HC in the exhaust gas and reduces NOx. Further, a filter 24 for
trapping PM is provided in the exhaust passage 21 at the downstream
side of the three-way catalyst device 23. An air-fuel ratio sensor
25 is arranged at the upstream side of the three-way catalyst
device 23 in the exhaust passage 21 to detect the oxygen
concentration of the gas flowing through the exhaust passage 21,
that is, the air-fuel ratio (air-fuel ratio detection value ABYF)
of the air-fuel mixture. Further, a catalyst outflow gas
temperature sensor 26 is arranged between the three-way catalyst
device 23 and the filter 24 in the exhaust passage 21 to detect a
catalyst outflow gas temperature THC, which is the temperature of
gas flowing out of the three-way catalyst device 23.
[0032] The engine 10 includes a controller 27. The controller 27 is
configured as a microcomputer including a calculation processing
circuit that executes calculation processes for control and a
memory that stores programs and data for control. The controller 27
receives detection signals from the airflow meter 16, the air-fuel
ratio sensor 25, and the catalyst outflow gas temperature sensor
26. Also, the controller 27 receives detection signals from a crank
angle sensor 28, which detects a crank angle .theta.c, or the
rotational angle of the crankshaft 14. Furthermore, the controller
27 receives detection signals from a vehicle speed sensor 29, which
detects a vehicle speed V, or the travelling speed of the vehicle,
and an accelerator position sensor 31, which detects an accelerator
operation amount ACC of an accelerator pedal 30. The controller 27
controls the opening degree of the throttle valve 17, the amount
and timing of the fuel injection of the fuel injection valve 18,
the timing of the spark of the ignition device 20 (ignition
timing), and the like, thereby controlling the operating state of
the internal combustion engine 10 in accordance with the driving
situation of the vehicle. The controller 27 also calculates the
rotational speed of the internal combustion engine 10 (engine
rotational speed NE) from the detection result of the crank angle
.theta.c by the crank angle sensor 28.
[0033] The controller 27 is connected to an onboard power supply 33
via an ignition switch 32. When the ignition switch 32 is switched
on (ignition is switched on), the onboard power supply 33 starts
supplying power to the controller 27. When the ignition switch 32
is switched off (ignition is switched off), the onboard power
supply 33 stops supplying power to the controller 27.
[0034] The controller 27 includes an air-fuel ratio control unit
27A, which performs an air-fuel ratio feedback control of the fuel
injection amount based on the air-fuel ratio detection value ABYF
of the air-fuel ratio sensor 25 during the combustion operation of
the internal combustion engine 10. The air-fuel ratio control unit
27A uses the difference of the air-fuel ratio detection value ABYF
from a target air-fuel ratio to control the air-fuel ratio of
air-fuel mixture burned in the cylinder 12 by operating an air-fuel
ratio feedback correction value FAF, which is one of the correction
values of the fuel injection amount of the fuel injection valve 18,
such that the difference approximates to zero. The air-fuel ratio
control unit 27A learns an air-fuel ratio learning value KG, which
is a correction value of the fuel injection amount, in accordance
with the air-fuel ratio feedback correction value FAF. The air-fuel
ratio control unit 27A learns the air-fuel ratio learning value KG
by gradually updating the air-fuel ratio learning value KG such
that the air-fuel ratio feedback correction value FAF approximates
to zero. When the air-fuel ratio feedback correction value FAF
stably remains around zero, the air-fuel ratio control unit 27A
completes the learning of the air-fuel ratio learning value KG to
stop updating the air-fuel ratio learning value KG. When, for
example, the air-fuel ratio feedback correction value FAF normally
deviates from zero after completion of learning, the air-fuel ratio
control unit 27A relearns the air-fuel ratio learning value KG.
Whether the learning of the air-fuel ratio learning value KG has
been completed is indicated by the state of an air-fuel ratio
learning flag. That is, the air-fuel ratio control unit 27A learns
the air-fuel ratio learning value KG (updates the value) as
described above when the air-fuel ratio learning flag is cleared.
After completion of the learning of the air-fuel ratio learning
value KG, the air-fuel ratio control unit 27A sets the air-fuel
ratio learning flag.
[0035] The controller 27 further includes a fuel introduction
processor 27B, which executes a fuel introduction process of
introducing air-fuel mixture containing fuel injected by the fuel
injection valve 18 without burning the air-fuel mixture in the
cylinder 12. In the present embodiment, the fuel introduction
processor 27B starts the fuel introduction process when the
following conditions (1) to (3) are all satisfied.
[0036] (1) The combustion operation of the internal combustion
engine 10 can be stopped. The fuel introduction process needs to be
performed with the combustion in the cylinder 12 stopped and
rotation of the crankshaft 14 kept. The controller 27 executes a
deceleration fuel cut-off to stop the fuel injection of the fuel
injection valve 18 of the internal combustion engine 10 and stops
the spark of the ignition device 20 while the vehicle is coasting.
It is determined that the combustion operation of the internal
combustion engine 10 can be stopped when the condition of executing
the deceleration fuel cut-off is satisfied. In the present
embodiment, when the accelerator operation amount ACC is zero and
the vehicle speed V is greater than or equal to a fixed value, it
is determined that the vehicle is coasting. After the deceleration
fuel cut-off is started, when the accelerator pedal 30 is depressed
to request re-acceleration of the vehicle or when the vehicle speed
V decreases to a specified return speed or lower, the controller 27
ends the deceleration fuel cut-off to resume the combustion
operation of the internal combustion engine 10.
[0037] (2) Increasing the temperature of the three-way catalyst
device 23 is requested. In the present embodiment, the fuel
introduction process is executed in order to burn and remove PM
deposited in the filter 24 by increasing the temperature of the
three-way catalyst device 23. The controller 27 estimates the
amount of PM deposited in the filter 24 from the operating state of
the internal combustion engine 10 and requests an increase
temperature of the three-way catalyst device 23 when the estimated
amount exceeds a certain value.
[0038] (3) Burned gas has been scavenged from the exhaust passage
21. Immediately after combustion in the internal combustion engine
10 is stopped, burned gas remains in the exhaust passage 21. In the
present embodiment, the fuel introduction process is started after
the burned gas in the exhaust passage 21 is replaced with air. In
the present embodiment, it is determined whether the burned gas has
been scavenged when the deceleration fuel cut-off continues for a
certain amount of time or longer.
[0039] FIG. 2 shows a procedure executed by the fuel introduction
processor 27B from the beginning to the end of such a fuel
introduction process. When the fuel introduction process is
started, it is first determined in step S100 whether a restriction
flag (described later) has been set. When the restriction flag has
been set (S100: YES), the current fuel introduction process is
ended.
[0040] When the restriction flag has not been set (S100: NO), the
process is advanced to step S110. In step S110, the fuel injection
of the fuel injection valve 18 is started. As described above, in
the present embodiment, when the deceleration fuel cut-off is
started and then burned gas in the exhaust passage 21 is scavenged,
the fuel introduction process is started. At this time, the spark
of the ignition device 20 is stopped. Thus, even if the fuel
injection of the fuel injection valve 18 is started, combustion is
not performed in the cylinder 12. Instead, air-fuel mixture
containing fuel injected by the fuel injection valve 18 is
introduced into the exhaust passage 21 without being burned in the
cylinder 12. The unburned air-fuel mixture introduced into the
exhaust passage 21 flows into the three-way catalyst device 23 and
burns in the three-way catalyst device 23. This burning generates
heat, thereby increasing the temperature of the three-way catalyst
device 23. As the temperature of the three-way catalyst device 23
increases, the temperature of gas flowing out of the three-way
catalyst device 23 and then into the filter 24 increases. When the
heat of the flowing high-temperature gas increases the temperature
of the filter 24 to the ignition point of the PM or higher, the PM
deposited in the filter 24 is burned and removed.
[0041] The fuel introduction processor 27B controls the fuel
injection amount of the fuel injection valve 18 in the following
manner. That is, when controlling the fuel injection amount during
the fuel introduction process, the fuel introduction processor 27B
first determines a catalyst fuel supply amount, which is the amount
of fuel supplied into the three-way catalyst device 23 per unit of
time, based on the intake air amount GA. During the fuel
introduction process, the three-way catalyst device 23 receives the
heat generated through the combustion of fuel in the three-way
catalyst device 23, and the heat is taken away from the three-way
catalyst device 23 by gas passing through the three-way catalyst
device 23. As the catalyst fuel supply amount increases, the amount
of the received heat increases. As the flow rate of the gas passing
through the three-way catalyst device 23 increases, the amount of
the heat to be taken away increases. During the fuel introduction
process, in which combustion is not performed in the cylinder 12,
the flow rate of the gas passing through the three-way catalyst
device 23 is approximately equal to the intake air amount GA. Thus,
in the present embodiment, in order to increase the temperature of
the three-way catalyst device 23 appropriately, the catalyst fuel
supply amount is determined so as to be larger when the intake air
amount GA is large than when the intake air amount GA is small.
Subsequently, the fuel introduction processor 27B calculates a
target injection amount, which is a target value of the fuel
injection amount of the fuel injection valve 18 for each injection
necessary for fuel pouring corresponding to the catalyst fuel
supply amount, based on the catalyst fuel supply amount and the
engine rotational speed NE. The fuel introduction processor 27B
sets, as the fuel injection amount (instructed injection amount)
set for the fuel injection valve 18, a value obtained by correcting
the target injection amount with the air-fuel ratio learning value
KG.
[0042] After starting the fuel injection in step S110, the fuel
introduction processor 27B repeatedly executes a determination
process of determining whether afterfire has occurred in step S120.
Afterfire refers to a phenomenon in which unburned air-fuel mixture
introduced into the exhaust passage 21 burns before flowing into
the three-way catalyst device 23. Afterfire is likely to occur when
the fuel concentration of unburned air-fuel mixture introduced into
the exhaust passage 21 is high. In the present embodiment, it is
determined whether afterfire has occurred based on the air-fuel
ratio detection value ABYF of the air-fuel ratio sensor 25. More
specifically, it is determined that afterfire has occurred when the
air-fuel ratio detection value ABYF is a value corresponding to a
richer air-fuel ratio than a specified rich determination value
.alpha..
[0043] After starting fuel injection, in a case in which the
determination that afterfire has occurred has never been made in
the repetition of the determination process in step S120 and the
combustion of the internal combustion engine 10 is requested to
resume due to depression of the accelerator pedal 30 or a decrease
in the vehicle speed V (S130: YES), the fuel introduction process
ends at the point in time the request is issued. At the same time
as when the fuel introduction process is ended, the combustion
operation of the internal combustion engine 10 is resumed.
[0044] When it is determined that afterfire has occurred before
combustion is requested to resume (S120: YES), the process is
advanced to step S140. When the process is advanced to step S140,
the restriction flag is set and an air-fuel ratio learning
completion flag is cleared in step S140. Further, in step S140, the
value of an AF counter, which indicates the number of times
afterfire has occurred, is incremented. Subsequently, in step S150,
the fuel injection is stopped and then the current fuel
introduction process is ended. That is, when it is determined that
afterfire has occurred during the execution of the fuel
introduction process, the fuel introduction process is stopped at
the point in time the determination is made. In this case, after
the fuel introduction process is stopped, the combustion of the
internal combustion engine 10 remains stopped until the combustion
is requested to resume.
[0045] The state of the restriction flag is cleared when the
ignition is turned off. The state of the air-fuel ratio learning
completion flag and the value of the AF counter are kept even when
the controller 27 stops supplying power after the ignition is
turned off. The value of the AF counter indicates the number of
times the fuel introduction process has been stopped in accordance
with the occurrence of afterfire after a vehicle is shipped or
after the controller 27 is initialized through repair or
inspection. The information of the number of times of stopping is
used for the purpose of, for example, identifying where fault
occurs during maintenance.
[0046] The operation and advantages of the present embodiment will
now be described.
[0047] FIG. 3 shows how the fuel introduction process is executed.
In FIG. 3, the combustion of the internal combustion engine 10
begins stopping at time t1, and the fuel introduction process is
started at time t2, which is subsequent to time t1. At time t4, the
combustion of the internal combustion engine 10 is resumed. At time
t3, when the fuel introduction process is started, afterfire
occurs.
[0048] As shown by the long dashed double-short dashed line in FIG.
3, when the fuel introduction process is continued until the
combustion is resumed, fuel continues to be introduced into the
exhaust passage 21 even after the occurrence of afterfire. Thus,
afterfire may continue until the fuel introduction process ends. As
compared to a slow combustion reaction in the three-way catalyst
device 23, afterfire is intense combustion. Thus, if afterfire
continues, the surface of the catalyst may be exposed to
high-temperature heat, thereby deteriorating the three-way catalyst
device 23. Additionally, if afterfire continues, annoying
combustion noises may be produced, thereby worsening the
drivability.
[0049] During execution of the fuel introduction process, in which
combustion is not performed in the cylinder 12, the oxygen
concentration of gas discharged from the cylinder 12 to the exhaust
passage 21 increases. During the period from when the fuel
introduction process starts to when afterfire occurs (t2 to t3),
gas having such a high oxygen concentration directly reaches a
detector of the air-fuel ratio sensor 25. Thus, the air-fuel ratio
detection value ABYF during this period indicates an air-fuel ratio
considerably leaner than that during the combustion operation of
the internal combustion engine 10. In FIG. 3, the air-fuel ratio
detection value ABYF during this period remains at a lean limit
value LL, which indicates an air-fuel ratio serving as the
lean-side limit of an air-fuel ratio detection range of the
air-fuel ratio sensor 25.
[0050] When afterfire occurs at time t3, the oxygen in the air-fuel
mixture is consumed through combustion, thereby reducing the oxygen
concentration of gas flowing around the detector of the air-fuel
ratio sensor 25. Thus, the air-fuel ratio detection value ABYF
changes from the lean limit value LL to a value corresponding to a
rich air-fuel ratio. In this manner, the change amount of the
air-fuel ratio detection value ABYF when afterfire does not occur
is greatly different from that when afterfire occurs. In the
present embodiment, a value that corresponds to a richer air-fuel
ratio than the rich-side limit value in a possible range of the
air-fuel ratio detection value ABYF when afterfire does not occur
and corresponds to a leaner air-fuel ratio than the lean-side limit
value in a possible range of the air-fuel ratio detection value
ABYF when afterfire occurs is set as the rich determination value
.alpha.. When the air-fuel ratio detection value ABYF becomes a
value that corresponds to a richer air-fuel ratio than the rich
determination value .alpha., it is determined through the
determination process that afterfire has occurred, thereby stopping
the fuel introduction process. This stops introducing fuel into the
exhaust passage 21 and thus stops afterfire.
[0051] In the present embodiment, during the execution of the fuel
introduction process, when it is determined that afterfire has
occurred in the determination process, the restriction flag is set.
The restriction flag remains set until ignition is switched off. In
a case in which the restriction flag is set when the fuel
introduction process starts, no substantial process is performed
and the fuel introduction process is ended. That is, when the fuel
introduction process is stopped in accordance with the
determination that afterfire has occurred, the fuel introduction
processor 27B restricts the fuel introduction process from being
further executed.
[0052] In some cases, even if the fuel introduction process is
stopped in accordance with the occurrence of afterfire, the cause
of afterfire is not identified. In such a case, afterfire is likely
to recur when the fuel introduction process is further executed. In
the present embodiment, when afterfire occurs during the fuel
introduction process, further execution of the fuel introduction
process is restricted until the ignition is turned off. This
prevents the recurrence of afterfire.
[0053] When the fuel concentration of air-fuel mixture introduced
into the exhaust passage 21 is high, afterfire is likely to occur.
The fuel introduction processor 27B sets the catalyst fuel supply
amount such that the fuel concentration of air-fuel mixture
introduced into the exhaust passage 21 does not become high enough
to produce afterfire. Thus, when afterfire occurs, the fuel
injection amount of the fuel injection valve 18 may be deviated
such that the actual injection amount is larger than the instructed
injection amount. In the present embodiment, the fuel injection
amount of the fuel injection valve 18 during the fuel introduction
process is corrected by the air-fuel ratio learning value KG, which
is learned during the combustion operation of the internal
combustion engine 10. Thus, when afterfire occurs during the
execution of the fuel introduction process, an improper value is
highly likely to be learned as the value of the air-fuel ratio
learning value KG. In the present embodiment, the fuel introduction
processor 27B clears the air-fuel ratio learning completion flag
when it is determined through the determination process that
afterfire has occurred. The air-fuel ratio control unit 27A learns
the air-fuel ratio learning value KG when the air-fuel ratio
learning completion flag is cleared. That is, the air-fuel ratio
control unit 27A relearns the air-fuel ratio learning value KG when
it is determined through the determination process that afterfire
has occurred. Accordingly, when afterfire has occurred during the
execution of the fuel introduction process and an improper value is
highly likely to be learned as the value of the air-fuel ratio
learning value KG, the air-fuel ratio learning value KG is
relearned.
Second Embodiment
[0054] An internal combustion engine according to a second
embodiment of the present invention will now be described in detail
with reference to FIG. 4.
[0055] In the first embodiment, when the fuel introduction process
is stopped in accordance with the occurrence of afterfire, the fuel
introduction processor 27B restricts the fuel introduction process
from being further executed. In the present embodiment, the fuel
introduction process is executed even after the fuel introduction
process is stopped in accordance with the occurrence of afterfire.
However, as described above, when afterfire has occurred, afterfire
is likely to recur when the fuel introduction process is further
executed. In the present embodiment, when the fuel introduction
process is stopped in accordance with the occurrence of afterfire,
the fuel injection amount of the fuel injection valve 18 is reduced
when the fuel introduction process is further executed. This
restricts the recurrence of afterfire.
[0056] FIG. 4 shows a procedure executed by the fuel introduction
processor 27B from the beginning to the end of the fuel
introduction process in the present embodiment. In the same manner
as the first embodiment, the fuel introduction processor 27B starts
the fuel introduction process when the conditions (1) to (3) are
all satisfied in the second embodiment.
[0057] When the fuel introduction process is started, it is first
determined in step S200 whether or not a reduction flag has been
set. As described below, the reduction flag is set when it is
determined that afterfire has occurred during the execution of the
fuel introduction process. The state of the reduction flag is
cleared when the ignition is turned off.
[0058] When the reduction flag is not set (S200: NO), 0 is set as
the value of a reduction correction amount in step S210. Then, the
process is advanced to step S230. When the reduction flag is set
(S200: YES), a specified positive value .beta. is set as the value
of the reduction correction amount in step S220. Then, the process
is advanced to step S230.
[0059] When the process is advanced to step S230, fuel injection is
started in step S230. In the present embodiment, when performing
the fuel injection, the fuel introduction processor 27B corrects,
with the air-fuel ratio learning value KG, the target injection
amount calculated from the catalyst fuel supply amount and the
engine rotational speed NE. Further, the fuel introduction
processor 27B sets, as the value of the instructed injection
amount, the difference obtained by subtracting the reduction
correction amount from the corrected value. As described above, 0
is set as the value of the reduction correction amount when the
reduction flag is not set, and the positive value .beta. is set as
the value of the reduction correction amount when the reduction
flag is set. Thus, the fuel injection amount of the fuel injection
valve 18 during the fuel introduction process is smaller when the
reduction flag is set than when the reduction flag is not set.
[0060] After starting the fuel injection, the fuel introduction
processor 27B repeatedly executes the determination process of
determining whether afterfire has occurred in step S240. In the
same manner with the first embodiment, in the present embodiment,
the determination process of determining whether afterfire has
occurred is performed based on the air-fuel ratio detection value
ABYF of the air-fuel ratio sensor 25.
[0061] After starting the fuel injection, in a case in which the
determination that afterfire has occurred has never been made in
the repetition of the determination process in step S240 and the
combustion resumption of the internal combustion engine 10 is
requested (S250: YES), the fuel introduction process ends at the
point in time the request is issued. At the same time as when the
fuel introduction process ends, the combustion operation of the
internal combustion engine 10 is resumed.
[0062] When it is determined that afterfire has occurred before the
combustion resumption is requested (S240: YES), the process is
advanced to step S260. When the process is advanced to step S260,
the reduction flag is set and the air-fuel ratio learning
completion flag is cleared in step S260. Further, in step S260, the
value of the AF counter is incremented. Subsequently, in step S270,
the fuel injection is stopped and then the current fuel
introduction process is ended. That is, when it is determined that
afterfire has occurred during the execution of the fuel
introduction process, the fuel introduction process is stopped.
[0063] When the fuel introduction process is executed again after
the fuel introduction process is stopped, the reduction flag has
already been set. Thus, the fuel introduction process is performed
with a reduced fuel injection amount of the fuel injection valve
18. As described above, afterfire is likely to occur when the fuel
injection amount of the fuel injection valve 18 is deviated such
that the actual injection amount is larger than the instructed
injection amount. Thus, reducing the fuel injection amount of the
fuel injection valve 18 restricts the recurrence of afterfire.
[0064] Determination Process for Occurrence of Afterfire
[0065] In the above-described embodiments, the determination
process of determining whether afterfire has occurred is performed
based on the air-fuel ratio detection value ABYF of the air-fuel
ratio sensor 25. Such a determination process does not have to be
performed in this manner.
[0066] FIG. 5 shows the arrangement of sensors other than the
air-fuel ratio sensor 25 that can be used for the determination
process. The determination process may be performed based on a
temperature detection value of an exhaust temperature sensor 34,
which is arranged at the upstream side of the three-way catalyst
device 23 in the exhaust passage 21. Alternatively, the
determination process may be performed based on a NOx concentration
detection value of a NOx sensor 35, which is arranged at the
downstream side of the three-way catalyst device 23 in the exhaust
passage 21.
[0067] FIG. 6 shows how the fuel introduction process is executed
when the determination process is performed based on the
temperature detection value of the exhaust temperature sensor 34.
In FIG. 6, the combustion of the internal combustion engine 10
begins stopping at time t11, and the fuel introduction process is
started at time t12, which is subsequent to t11. At time t14, the
combustion of the internal combustion engine 10 is resumed. At time
t13, when the fuel introduction process is started, afterfire
occurs.
[0068] When the combustion of the internal combustion engine 10 is
stopped, the temperature of gas flowing through the exhaust passage
21 decreases. Thus, during the period from when the fuel
introduction process starts to when afterfire occurs (t12 to t13),
the temperature detection value of the exhaust temperature sensor
34 indicates a temperature lower than that during the combustion
operation of the internal combustion engine 10. When afterfire
occurs, the temperature of gas increases at a section where the
afterfire occurs. Thus, when the temperature detection value of the
exhaust temperature sensor 34 is greater than or equal to a
specified determination value, it can be determined that afterfire
has occurred. That is, there is deviation between a possible range
of the temperature detection value when afterfire occurs and a
possible range of the detection value when afterfire does not
occur. Thus, the determination of whether afterfire has occurred
can be made based on the temperature detection value by setting, as
the determination value, a temperature higher than the maximum
value of the possible range of the temperature detection value when
afterfire does not occur and lower than the minimum value of the
possible range of the temperature detection value when afterfire
occurs. When the determination process is performed using the
temperature detection value of the exhaust temperature sensor 34 in
such a manner, afterfire is restricted from continuing by stopping
the fuel introduction process in accordance with the occurrence of
afterfire at time t13.
[0069] FIG. 7 shows how the fuel introduction process is executed
when the determination process is performed based on the NOx
concentration detection value of the NOx sensor 35. In FIG. 7, the
combustion of the internal combustion engine 10 begins stopping at
time t21, and the fuel introduction process is started at time t22,
which is subsequent to t21. At time t24, the combustion of the
internal combustion engine 10 is resumed. At time t23, when the
fuel introduction process is started, afterfire occurs.
[0070] NOx, which is a product formed when air-fuel mixture is
burned, is scarcely generated in a slow combustion in the three-way
catalyst device 23 during the fuel introduction process. In
contrast, a large amount of NOx is generated through an intense
combustion of afterfire. The combustion in afterfire is performed
at an air-fuel ratio leaner than a stoichiometric air-fuel ratio.
The gas flowing into the three-way catalyst device 23 through this
combustion contains little reduction components of NOx. Thus, a
large amount of NOx generated in afterfire directly passes through
the three-way catalyst device 23 without being reduced in the
three-way catalyst device 23, thereby increasing the NOx
concentration detection value of the NOx sensor 35 with the
occurrence of afterfire. Thus, when the NOx concentration detection
value of the NOx sensor 35 is greater than or equal to a specified
determination value, it can be determined that afterfire has
occurred. That is, there is deviation between a possible range of
the NOx concentration detection value when afterfire occurs and a
possible range of the NOx concentration detection value when
afterfire does not occur. Thus, the determination of whether
afterfire has occurred can be made based on the NOx concentration
detection value by setting, as the determination value, a
concentration higher than the maximum value of the possible range
of the NOx concentration detection value when afterfire does not
occur and lower than the minimum value of the possible range of the
NOx concentration detection value when afterfire occurs. When the
determination process is performed using the NOx concentration
detection value of the NOx sensor 35 in such a manner, afterfire is
restricted from continuing by stopping the fuel introduction
process in accordance with the occurrence of afterfire at time
t23.
[0071] The above-described embodiments may be modified as follows.
The above-described embodiments and the following modifications can
be combined as long as the combined modifications remain
technically consistent with each other.
[0072] In the above-described embodiments, when afterfire has
occurred during the execution of the fuel introduction process, an
improper value is likely to be learned as the air-fuel ratio
learning value KG, that is, the air-fuel ratio learning value KG is
likely to be learned incorrectly. In such a case, the air-fuel
ratio learning value KG is then relearned. In some cases, for
example, in a case in which the air-fuel ratio learning value KG is
not learned or in a case in which the air-fuel ratio learning value
KG is not reflected on the fuel injection amount during the fuel
introduction process even if the learning is performed, the
incorrect learning of the air-fuel ratio learning value KG is not a
factor of the occurrence of afterfire during the execution of the
fuel introduction process. Also, in some configurations of the
internal combustion engine, factors other than the incorrect
learning of the air-fuel ratio learning value KG cause afterfire
during the execution of the fuel introduction process. In such a
case, the air-fuel ratio learning value KG does not have to be
relearned when the fuel introduction process is stopped in
accordance with the occurrence of afterfire.
[0073] In the above-described embodiments, the fuel introduction
processor 27B uses the AF counter to record, as diagnostic
information, the number of times the fuel introduction process has
been stopped in accordance with the determination result of the
determination process. However, the number of times of such
stopping does not have to be recorded.
[0074] In the above-described embodiments, unburned air-fuel
mixture is introduced into the exhaust passage 21 by performing
fuel injection with the spark of the ignition device 20 stopped.
The timing at which the spark of the ignition device 20 can ignite
the air-fuel mixture in the cylinder 12 is limited to a period
close to the compression top dead center. That is, there is a
period in which air-fuel mixture does not burn in the cylinder 12
even if the spark is generated. Thus, the fuel introduction of
introducing unburned air-fuel mixture into the exhaust passage 21
can also be executed by performing fuel injection while generating
the spark of the ignition device 20 during such a period.
[0075] In the above-described embodiments, the fuel introduction
process is performed for the purpose of burning and removing PM
deposited in the filter 24. Instead, the fuel introduction process
may be performed to increase the temperature of the three-way
catalyst device 23 for other purposes. For example, a catalyst
temperature-increasing control may be performed to restore the
exhaust purification performance of the three-way catalyst device
23 when the exhaust purification performance is reduced due to a
decrease in the catalyst temperature.
[0076] In the above-described embodiments, the fuel introduction
process is performed while the vehicle is coasting. However, the
fuel introduction process may be performed under conditions other
than coasting of the vehicle as long as the rotation of crankshaft
14 can be maintained with combustion in the internal combustion
engine 10 stopped. Some hybrid vehicles having a motor as a drive
source in addition to an internal combustion engine are capable of
rotating the crankshaft with the driving force of the motor while
the combustion operation of the internal combustion engine is
stopped. In such hybrid vehicles, the fuel introduction process can
be performed while rotating the crankshaft with the driving force
of the motor.
[0077] In the above-described embodiments, the fuel introduction
process is executed by injecting fuel into the intake passage 15
using the fuel injection valve 18. Alternatively, the fuel
introduction process can be executed through fuel injection into
the cylinders 12 in an internal combustion engine equipped with
fuel injection valves of a direct injection type, which injects
fuel into the cylinders 12.
[0078] The controller 27 is not limited to a device that includes a
CPU and a memory and executes software processing. For example, at
least part of the processes executed by the software in the
above-described embodiments may be executed by hardware circuits
dedicated to execution of these processes (such as ASIC). That is,
the controller may be modified as long as it has any one of the
following configurations (a) to (c). (a) A configuration including
a processor that executes all of the above-described processes
according to programs and a program storage device such as a ROM
that stores the programs. (b) A configuration including a processor
and a program storage device that execute part of the
above-described processes according to the programs and a dedicated
hardware circuit that executes the remaining processes. (c) A
configuration including a dedicated hardware circuit that executes
all of the above-described processes. A plurality of software
processing circuits each including a processor and a program
storage device and a plurality of dedicated hardware circuits may
be provided. That is, the above processes may be executed in any
manner as long as the processes are executed by processing
circuitry that includes at least one of a set of one or more
software processing circuits and a set of one or more dedicated
hardware circuits.
[0079] Various changes in form and details may be made to the
examples above without departing from the spirit and scope of the
claims and their equivalents. The examples are for the sake of
description only, and not for purposes of limitation. Descriptions
of features in each example are to be considered as being
applicable to similar features or aspects in other examples.
Suitable results may be achieved if sequences are performed in a
different order, and/or if components in a described system,
architecture, device, or circuit are combined differently, and/or
replaced or supplemented by other components or their equivalents.
The scope of the disclosure is not defined by the detailed
description, but by the claims and their equivalents. All
variations within the scope of the claims and their equivalents are
included in the disclosure.
* * * * *